f2fs: avoid overflow when large directory feathure is enabled
When large directory feathure is enable, We have one case which could cause
overflow in dir_buckets() as following:
special case: level + dir_level >= 32 and level < MAX_DIR_HASH_DEPTH / 2.
Here we define MAX_DIR_BUCKETS to limit the return value when the condition
could trigger potential overflow.
Changes from V1
o modify description of calculation in f2fs.txt suggested by Changman Lee.
Suggested-by: Changman Lee <cm224.lee@samsung.com>
Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/include/linux/f2fs_fs.h b/include/linux/f2fs_fs.h
index 8c03f71..ba6f312 100644
--- a/include/linux/f2fs_fs.h
+++ b/include/linux/f2fs_fs.h
@@ -394,6 +394,9 @@
/* MAX level for dir lookup */
#define MAX_DIR_HASH_DEPTH 63
+/* MAX buckets in one level of dir */
+#define MAX_DIR_BUCKETS (1 << ((MAX_DIR_HASH_DEPTH / 2) - 1))
+
#define SIZE_OF_DIR_ENTRY 11 /* by byte */
#define SIZE_OF_DENTRY_BITMAP ((NR_DENTRY_IN_BLOCK + BITS_PER_BYTE - 1) / \
BITS_PER_BYTE)